Time Keeping

[dunkuk2k]

Hi, I just wanted to confer on how well some of these old beauties actually perform / keep time. I have just recently (November 9th) received my G/F TC2 which I am chuffed to bits with, seems to be keeping very good time so far. I think I will run it for a month to see how it performs.

I checked the module out when I received it on Wednesday, to make sure It had not been mis-sold/been bodged with pulsar innards etc... and it was amazingly clean inside and for its age the same outside too. Really looks like it's never been used save for a little dirt between the links. It set really easily baring in mind I'd never set a watch using a magnet before, so its so far so good!

I also have a pulsar P4 which I've had about 12 months and generally it keeps very good time. However it is a little temperamental and I've seen it lose a number of hours / date reset etc...every couple of months.

Dunk

[bruce wegmann]

This has been discussed before, but merits a re-visit. Quartz crystal-controlled oscillators are very stable, but not absolutely stable. Even in a zero-temperature-change environment, they will drift in frequency over a long period. Though this phenominon is well-known, the precise reasons for it are less well understood. As crystals "age", their resonant frequency shifts (some up, some down, and never "change direction" once the process starts). The rate of drift is initially high (relatively speaking), then slows over a period of months or years along what could be loosely described as a decay curve. This process only occurrs while the crystal is actually under power, and drops to near-zero values after a few years, at most. The overall effect of this is that, unlike mechanical watches, quartz watches keep BETTER time (in terms of stability) as they get older. Set to zero error at a moderate temperature (say, 68-72 deg. F., or 20-22 deg. C.) I have Pulsars that have gained or lost no more than 8 or 10 seconds in a year, well within the original timekeeping specification of + or - 5 seconds a month, or 1 minute a year. Thats better than 2 parts per million of stability guaranteed (10 seconds of error actually works out to .3 part per million, or 300 parts per billion). Not bad for a mid-70s piece of commercial electronics...

[dunkuk2k]

Hi Bruce, thanks for your response.Hopefully that will give us all confidence as long as these things are "ticking" they will remain accurate!

I guess a lot of mechanical watches would be lucky to achieve +/- 5 seconds a day let alone per month! I must be a bit of a purist of sorts as I can't imagine owning an analogue display watch with a quartz movement, despite them being more accurate!

I believe these Omega's have in essence the same module as the date 2 and date command/P3 pulsars, I am curious whether the factories would have set-up all of these installs in each model or brand to the same specification/tolerance?

[bruce wegmann]

All the Pulsar, Hamilton, and Omega TC modules came off the same production line (at the Time Computer facility in Lancaster, PA), and so have identical operational characteristics. The early P2 (201-1) modules (which were also used to retrofit most of the P1s) had only a single trimmer of limited adjustment, and many of the timing crystals have now drifted beyond the range of their ability to keep the frequency within specified accuracy (which is why most P1s don't keep very good time any more ). The second-generation P2 modules (201-2, with the horizontal light sensor), had a second, wider-range ("coarse") trimmer on the front of the circuit board, and most of these can still be adjusted back to within the original 60sec/year tolerance. The smaller ("fine") trimmer on the back of the module above the battery compartments can be used to accurately bring the frequency error to near-zero. Extreme frequency drift (I have seen 200+ sec/month) would require replacing the quartz crystal itself...fortunately, not a complicated repair, except, of course, the P1, which would require seperating the case halves (not a job for the inexperienced!). Roughly 75% of the known P1s have the earlier 201-1 module; a few probably even left Lancaster with the later 201-2. All modules were subjected to a week-long "burn-in" at the factory before being assembled into complete watches. This was intended to catch early failures (the so-called "infant mortality" factor), and identify modules that were drifting in frequency at an excessive rate (in either direction), so as to keep failures "in the field" at a minimum.

[dunkuk2k]

well after 1 month my watch lost just under 5 seconds, i guess that stands up pretty well for a 37 year old watch!

[bruce wegmann]

Time Computer produced a monitoring instrument (the "Pulsar Analyzer") that read the quartz signals directly, compared them with a calibrated internal frequency standard, and gave a readout on a meter in seconds/month of how fast or slow the watch was running. The trimmers could be adjusted while the watch was on the meter, and it took less than a minute to zero-out the frequency error (quartz frequency on the Pulsar/Hamilton/Omega TC modules was nominally 32,768 Hz, or cycles-per-second). Years later, Zantech (founded by Louis Zanoni...of Optel fame) introduced an improved version that had a wider plus-and-minus range, and gave the results in a digital readout (I have three of these...a must-have tool for those obsessed with accuracy). Both of these still show up occasionally on eBay. Much better than waiting a month to see how much you're gaining or losing.
BTW, for those curious about just how far that obsession can go, you should visit leapsecond.com , maintained by a guy who probably has the most accurate timepieces in the country. He started out wanting a second a year; his latest attempt (multiple atomic hydrogen masers in tandem) gains or loses 1 second in 1.5 million years (as he puts it; a cumulative drift of about two nanoseconds a day...1.826, to be exact). As good as that sounds, it is crushingly eclipsed by the latest generation of atomic standards, with an error of 1 second in 250 milliion years...a single tick of the clock off since the appearance of the first dinosaurs.

[rewolf]

...visit leapsecond.com , maintained by a guy who probably has the most accurate timepieces in the country...

... and the only genuine atomic wristwatch I've ever seen